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Originally posted by SALEENGTSPORT:
ENGINE LIGHT 1993 GT FOXBODY
STUMBLES JERKS SOMETIME WHEN ENGINE GETS WARM RUNS BETTER THINK HAS SOMETHING TO DO WITH THE EGR NO FLOW.

TROUBLE CODES: 33. 41. 66. 91.

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33 is "EGR valve open not detected"
41 is "No HEGO switch detected always lean (right O2)
66 is "MAF or VAF below minimum voltage"
91 is "No HEGO switch detected (left O2)"

Sounds like you have a few problems
 

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Posted by CA FiveOh (Member # 7429) on :
 
I wouldn't worry all that much with the EGR code, but the MAF volts below minimum is one to worry about. Once you get that code, a check engine light will occur and the EEC will enter what's known as limp mode. In limp mode, timing is retarded, and fuel is based off a 'safe' table that is richer than normal. This is fairly common with calibrations of 42lb or larger, so if that is not the case for you then I would say that it's possible you have a bad MAF sensor.
 

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Posted by JohnB (Member # 969) on :
 
Either hook up your O2's or change them and clean your MAF.
 

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